1. Field of the Invention
The present invention relates to a display device that displays an image on a display screen of a liquid crystal display panel.
2. Description of the Related Art
Display devices configured such that an image is displayed on a display screen of a liquid crystal display panel are known. In a display device having a liquid crystal display panel, the response speed of liquid crystal varies in accordance with variations in the temperature of the liquid crystal display panel due to changes in the ambient temperature or internal temperature of the display device. Hence, the variations in the response speed of liquid crystal may cause variations in the speed of switching between images on the display screen of the liquid crystal display panel or may cause variations in the motion on a moving image. For this reason, a display device of the related art (Japanese Unexamined Patent Application Publication No. 2005-4203) is configured to store compensation data in advance in a memory in association with temperatures, read the compensation data associated with the actual temperature from the memory when displaying an image, and control gray-scale data representing the image using the compensation data to correct for a reduction in response speed. This display device can suppress variations in the response speed of liquid crystal in a liquid crystal display panel, and provide stable display of an image (still image, moving image) on a display screen of the liquid crystal display panel.
A display device is available which includes a movable member arranged to face a display screen of a liquid crystal display panel and which is configured such that the movable member is moved and an image object displayed on the display screen is moved accordingly so that the movable member and the image object displayed on the display screen are associated with each other. For example, an on-vehicle display device (“cluster display device”) is available which, as illustrated in FIGS. 1A and 1B, includes a first movable semi-circular frame member 20a and a second movable semi-circular frame member 20b which are shaped in semi-circular arcs. The first movable semi-circular frame member 20a and the second movable semi-circular frame member 20b are arranged to face a display screen 120 of a liquid crystal display panel 12. The first movable semi-circular frame member 20a and the second movable semi-circular frame member 20b are linearly moved and a first image object IOa of a speedometer and a second image object IOb of a tachometer, which are displayed on the display screen 120, are moved accordingly so that the first movable semi-circular frame member 20a and the first image object IOa (i.e., the speedometer) displayed on the display screen 120 are associated with each other and the second movable semi-circular frame member 20b and the second image object IOb (i.e., the tachometer) displayed on the display screen 120 are associated with each other. Such an on-vehicle display device provides a user with the image objects IOa and IOb (i.e., the speedometer and the tachometer) displayed on the display screen 120 of the liquid crystal display panel 12 as live views displayed integrally with the movable members (i.e., the first movable semi-circular frame member 20a and the second movable semi-circular frame member 20b).
In such a display device, it is desirable that the relative positions of the movable members with respect to the display screen of the liquid crystal display panel be detected. Using the relative positions allows the image objects to be displayed on the display screen of the liquid crystal display panel so that the positions of the image objects match the detected positions of the movable members, and also allows the movable members to move so that the detected positions of the movable members are associated with the positions of the image objects displayed on the display screen. The positions of the movable members may generally be detected using a potentiometer such as a linear position sensor (LPS).
The resistance of a potentiometer such as an LPS may vary due to temperature changes, and may also change with time. For this reason, it is desirable that corrected data for resistance values be stored in advance in association with temperatures in order to accurately detect the positions of the movable members using a potentiometer. In addition, it is also desirable that relationships between the positions and the resistance values be calibrated each time the potentiometer is used for a certain duration of time.
In order to move a movable member and move an image object displayed on the display screen accordingly so that the movable member and the image object displayed on the display screen are accurately associated with each other, as described above, a large amount of corrected data is required to correct the response speed of liquid crystal, and a large amount of corrected data is also required to correct the resistance of the potentiometer. Additionally, the characteristics of changes in the response speed of liquid crystal in accordance with temperature changes may differ depending on the type of liquid crystal (for example, twisted nematic (TN), vertical alignment (VA), or in-plane switching (IPS)). Hence, in terms of such types of liquid crystal, a larger amount of corrected data may be required. It is therefore difficult to move a movable member and move an image object displayed on a display screen accordingly so that the movable member and the image object displayed on the display screen are accurately associated with each other.